Obesity is a condition characterized by an increase in body fat content resulting in excess body weight above accepted norms. Obesity is among the most important nutritional disorders in the western world and represents a major health problem in many industrialized countries. This disorder can lead to increased mortality due to increased incidences of diseases such as cardiovascular disease, digestive disease, respiratory disease, cancer and type 2 diabetes. Searching for compounds that reduce body weight has been going on for many decades. One line of research includes the activation of serotoninergic systems, either by direct activation of serotonin receptor subtypes or by inhibiting serotonin reuptake. The exact receptor subtype profile required is however not believed to be known.
Serotonin (5-hydroxytryptamine or 5-HT) is considered to be a key transmitter of the peripheral and central nervous system and is believed to modulate a wide range of physiological and pathological functions, including, for example, anxiety, sleep regulation, aggression, feeding and depression. The identification and cloning of multiple serotonin receptor subtypes have been reported. The cloning of the 5-HT6 receptor was reported by several groups in 1993. See, e.g., (Ruat, M. et al. (1993) Biochem. Biophys. Res. Commun. 193: 268-276; Sebben, M. et al. (1994) NeuroReport 5: 2553-2557). This receptor is believed to be positively coupled to adenylyl cyclase and has been shown to display affinity for neuroleptics such as clozapine. Recently, the effect of 5-HT6 antagonist and 5-HT6 antisense oligonucleotides to reduce food intake in rats has been reported. See, e.g., (Bentley, J. C. et al. (1999) Br J. Pharmacol. Suppl. 126, P66; Bentley, J. C. et al. (1997) J. Psychopharmacol. Suppl. A64, 255; Woolley M. L. et al. (2001) Neuropharmacology 41: 210-219).
Compounds with enhanced affinity and selectivity for the 5-HT6 receptor have been identified, e.g. in WO 00/34242 and by Isaac, M. et al. (2000) 6-Bicyclopiperazinyl-1-arylsulphonylindoles and 6-Bicyclopiperidinyl-1-arylsulphonylindoles derivatives as novel, potent and selective 5-HT6 receptor antagonists. Bioorganic & Medicinal Chemistry Letters 10: 1719-1721 (2000), Bioorganic & Medicinal Chemistry Letters 13: 3355-3359 (2003), Expert Opinion Therapeutic Patents 12(4) 513-527 (2002).